The present invention relates to a sawing system having a plurality of rotating saw blades adapted to cut or saw, substrates or semiconductor wafers, in two opposite directions of relative movement at a sawing zone, and more particularly to a sawing system having a vision zone incorporated between a loading/unloading zone and the sawing zone.
A singulation saw, hereinafter referred to as a sawing system, for sawing either substrate or semiconductor wafers using a pair of counter rotating saw blades is disclosed in co-pending patent application Ser. No. 09/849,049 titled xe2x80x9cBI-DIRECTIONAL SINGULATION SAW AND METHODxe2x80x9d filed on May 5, 2001, and assigned to the same assignee as the present patent application, and which is incorporated herein by reference thereto.
With reference to FIG. 1, the disclosed sawing system 100 is coupled to a prior art handler 105, and the disclosed sawing system 100 primarily comprises three processing zones. The three processing zones are physically arranged relative to each other with a sawing zone 110 located between a loading/unloading zone 115, and a vision zone 120. A dual spindle counter rotating saw 125 is used in the sawing zone 110, and a vision system 129 that employs a camera is employed in the vision zone 120.
A transport system transports the substrates or semiconductor wafers between the unloading/unloading zone 115, the sawing zone 110, and the vision zone 120; and the transport system also transports the substrates or semiconductor wafers in a reciprocating movement during the sawing process in the sawing zone 110. The transport system comprises a pair of linear transport means that transport two rotatable carrier supports 122 and 124 along transport paths 129 and 130, respectively. Each of the two rotatable carrier supports 122 and 124 are adapted for loading a removable carrier thereon. The substrates or semiconductor wafers for sawing are removably mounted on one such carrier.
During the sawing process, for example, when singulating a semiconductor wafer, the handler 105 loads a carrier, with the semiconductor wafer thereon, at the loading/unloading zone 115 onto one of the carrier supports 122 of the sawing system 100. The transport system then transports the wafer past the sawing zone 110, to the vision zone 120. After the vision system 129 has captured the necessary images of the wafer for alignment purposes and the like, the transport system then transports the wafer from the vision zone 120 to the sawing zone 110. At the sawing zone 110, the wafer is singulated by the dual spindle counter rotating saw 125, using the alignment information from the vision system. The dual spindle counter rotating saw 125 is movably mounted along the Y and Z axes, and the rotatable carrier support 122 allows the wafer to be sawn along the X and Y axes. When the dual spindle counter rotating saw 125 has completed singulation of the wafer, the singulated wafer is transported by the transport system to the loading/unloading zone 115, where the carrier with the singulated wafer thereon is unloaded from the carrier support 122 at the loading/unloading zone 115 by the handler 105.
The transport system can transport two wafers at a time such that, while a first wafer on the carrier support 122 is being singulated in the sawing zone 110, a second wafer on the other carrier support 124 is transported from the loading/unloading zone 115 to the vision zone 120, where the necessary images of the wafer are captured. Then, after the first wafer has been singulated in the sawing zone 110, as the first wafer is being transported from the sawing zone 110 to the loading/unloading zone 115, the second wafer at the vision zone 120 is transported to the sawing zone 110 and sawing of the second wafer can then begin.
A disadvantage of this arrangement is that the second wafer passes the sawing zone 110 while the first wafer is being sawn. Consequently, as the sawing process involves the use of water to cool the saw blades as well as to wash away debris, the water from the sawing process tends to wet the second wafer, which adversely affects the subsequent imaging of the second wafer in the vision zone 120.
In order for the transportation system to be able to transport substrates or semiconductor wafers between the loading/unloading zone 115 and the vision zone 120, the dual spindle counter rotating saw 125 in the sawing zone 110 is mounted on a cantilever arrangement. The cantilevered dual spindle counter rotating saw 125 is movably mounted to travel along a Y-axis relative to the transport system, and also movably mounted to extend along a Z-axis for moving to and away from the substrate or wafer to be sawn. Due to the weight of the dual spindle counter rotating saw 125, the load on the cantilever varies dependent upon the position of the saw motor assembly along the Y-axis. Consequently, the displacement of the saw assembly away from a reference horizontal plane also varies. Hence, a disadvantage of the cantilever mounted dual spindle counter rotating saw 125 is the tendency of variation in the displacement of the saw blades, and this variation adversely affects the required five micron tolerance for a cut made by the saw blades.
A scrap removal system of the sawing system 100 operates during the sawing process, where water washes various debris in the sawing zone 110 down a debris collection sink to a removable bin, where the debris is separated from the water. The bin containing the debris can then either be emptied and re-attached to the sawing system 100, or replaced with an empty bin. A disadvantage of this scrap removal system is the need to stop the sawing process prior to removing the bin, in order stop the flow of water and debris to the bin, and allow the bin containing the debris to be physically removed from the sawing system 100, without spilling water and debris in a production area. Consequently, the need to stop the sawing process reduces the throughput of the sawing system 100.
The present invention seeks to provide a bi-directional singulation saw and method, which overcomes or at least reduces the abovementioned problems of the prior art.
Accordingly, in one aspect, the present invention provides a bi-directional singulation system for singulation of substrates, the bi-directional singulation system comprising:
a loading/unloading zone for mounting a carrier onto a first movable carrier support located thereat prior to singulation of at least one substrate disposed on the carrier, and the loading/unloading zone for unloading the carrier from the first movable carrier support located thereat after singulation of the at least one substrate;
a sawing zone comprising at least one bi-directional cutting means for singulating at least another substrate on another carrier mounted on a second movable carrier support, while the first movable carrier support is at the loading/unloading zone; and
a vision zone located between the loading/unloading zone and the sawing zone, the vision zone comprising a vision system for imaging the at least one substrate when the first movable carrier support is at the vision zone, while the second movable carrier support is at the sawing zone.
In another aspect the present invention provides a method for singulating substrates with a bi-directional singulation system, the method comprising the steps of:
a) providing a bi-directional singulation system comprising:
a loading/unloading zone for mounting a first carrier onto a first movable carrier support and for unloading the first carrier from the first movable carrier support, and the loading/unloading zone for mounting a second carrier onto a second movable carrier support and for unloading the second carrier from the second movable carrier support;
a sawing zone comprising at least one bi-directional cutting means for singulating at least a first substrate and at least a second substrate; and
a vision zone located between the loading/unloading zone and the sawing zone, the vision zone comprising a vision system for imaging the at least the first substrate and for imaging the at least the second substrate;
b) while singulating the at least the first substrate on the first movable carrier support at the sawing zone to produce the at least the first singulated first substrate, performing the steps of:
b1) mounting the second carrier with the at least the second substrate thereon on the second movable carrier support at the loading/unloading zone; and
b2) imaging the at least the second substrate on the at least the second movable carrier support at the vision zone; and
c) while singulating the at least the second substrate on the second movable carrier support at the sawing zone to produce the at least the second singulated substrate, performing the steps of:
c1) unloading the first carrier with the at least the first singulated substrate thereon on the first movable carrier support at the loading/unloading zone;
c2) mounting another carrier with at least another substrate thereon on the first movable carrier support at the loading/unloading zone; and
c3) imaging the at least another substrate on the at least the first movable carrier support at the vision zone.
In yet another aspect the present invention provides a scrap removal system for removing debris in a bi-directional singulation system, the scrap removal system comprising:
a conveyor located substantially within a sawing zone of the bi-directional singulation system, the conveyor having an internal portion for to receive debris from a sawing process, and the conveyor having an external portion that extends outwardly away from the sawing zone, the conveyor for transporting the debris from the internal portion to the external portion for disposal.